None.
The invention is a radiant energy collection instrument. More specifically, the invention is a fiber optic sensor using a pneumatically driven shutter to shield the sensor.
Chemical processing systems using radiant energy sources are known in many industrial processes. These chemical processing systems typically use ultraviolet (UV) lamps or bulbs placed near a product in a manufacturing line to cause chemical reactions to occur in or on the product. Often these chemical reactions are referred to as curing or in some industries as drying. The wavelengths of radiant energy radiated by UV lamps (in the visible and non-visible spectrum) have been found to be particularly effective in transferring energy to the product to effect the desired chemical changes.
The wavelengths radiated onto the product typically range from approximately 2.5 micrometers to approximately 190 Nanometers. The product being processed by the system can be almost anything, but typically it is a xe2x80x9cwebxe2x80x9d of paper, plastic, or paper-like material (e.g., paperboard). The xe2x80x9cwebxe2x80x9d comprises a continuous stream of material fed through a series of rollers. Radiant energy sources (typically more than one lamp or bulb) are placed at various points along the web to radiate energy onto the web. Coatings on the surface of the web, or the web material itself is caused to undergo a chemical change during this process. In this manner the coatings on the web (e.g., ink, lacquer, or adhesives) or the web itself is cured.
Unfortunately, the performance of an individual UV energy lamp can vary over its lifetime. A newer lamp may radiate energy more intensely than when it is older. Additionally, individual lamps with the same specifications can perform differently. Specifically, different wavelengths may be emitted more intensely from one lamp to the next. As would be expected, as a lamp grows older, its performance typically declines until it ultimately fails. The power provided to the lamp can also affect the lamp performance. If the electrical service to the lamp fluctuates, specific wavelengths produced by the lamp may vary in intensity. Differences in air temperature surrounding the lamp as well as the time it takes for the lamp to warm up may also cause fluctuations in wavelength intensity. All these variances in the intensity of the radiant energy emitted by the lamp can cause the level of drying and curing of the web to vary. Therefore, in order to optimize the process and provide consistent product it is necessary to monitor the amount of radiant energy emitted by the lamp in order to assure that proper drying and curing time is provided to the web.
To measure the amount or xe2x80x9cdosexe2x80x9d of radiant energy impinging on the web, a detection system is needed. In the past, many methods of measuring this amount of radiant energy have been used. One previous method to evaluate whether the energy lamps were providing adequate radiant energy was to test the web downstream from the lamp. Although this gave a very accurate measurement of whether the web had been properly cured, the measurement took place too late in the process, since product which had not been properly cured could not be used and was wasted and discarded.
An alternate measurement method was to use electronic devices such as xe2x80x9clight pucksxe2x80x9d (known in the art) placed on the web and moved with the web between the lamp and the web to provide a test measurement of the amount of radiant energy being emitted by the lamps. While this method gave a more direct measurement of lamp performance, it was performed during setup and not during actual production so that no information was being gathered as to energy impinging the web during the actual run time process. In particular, no measurements of variances in the radiant energy impinging the web were able to be taken. Once again, improperly cured product resulted.
To avoid this waste of product, a second method was developed which monitored the energy draw of the power supply for each lamp, in an attempt to provide a xe2x80x9creal timexe2x80x9d measurement of the actual energy used by the lamp. This measurement was a very rough and inaccurate way to estimate the amount of radiant energy emitted by the lamp and impinging on the web on a continuous basis. Although inaccurate, this method was an attempt to determine how much radiant energy was impinging onto the web in xe2x80x9creal timexe2x80x9d. Measuring the radiant energy in xe2x80x9creal timexe2x80x9d made it possible to more accurately control the curing time of the web (e.g., by changing the pace of the web through the process to provide longer or shorter drying time) and reduce loss of product. Unfortunately, many factors made the measurement of the energy drawn from the lamp an inaccurate measurement of the radiant energy impinging the web defeating any advantages gained by the real time measurements. For example, as the lights themselves degraded due to aging, the amount of energy drawn by the lamp could change relative to the amount of radiation emitted. Additionally, the radiation emitted for a specific amount of power drawn varied from lamp to lamp. To alleviate these problems, electronic detection devices were placed around the lamp to measure the direct output of radiant energy emitted from the lamp. However, the environmental conditions surrounding the process (e.g., high humidity, high temperature, RF radiation, and foreign objects such as airborne adhesive, lacquer, etc.) often caused the electronics in the detectors to break down and malfunction.
Finally, remote collection devices have been developed which allow the radiant energy emitted by the lamp to be collected and transported (typically by fiber optic cables) to a detection device placed remotely from the hostile environment surrounding the web. These devices were placed on the back side of the lamp (opposite the web), allowing a direct measurement of the amount of radiant energy emitted by the lamp to be taken. This placement of these devices on the opposite side of the lamp from the web was done for two main reasons: first there was very little space between the web and the lamp and second because the most hostile environment in the process is directly between the web stream and the surface of the lamp housing. The space between the web and the lamp was small in order to keep contaminants such as oxygen (which can affect curing of the web in some processes) to a minimum, as well as assuring that a maximum amount of radiant energy from the lamps impinged the web. The environment is extremely hostile at this positioning since it is most directly in contact with the radiation and heat from the lamp as well as the adhesive and airborne contaminants from the web.
While remote collection devices solved some of the problems described above, they still did not deliver accurate measurements of radiant energy intensity impinging the web. Typically, a transparent cover is placed over the lamp in order to protect the lamp elements from airborne contaminants. This transparent cover becomes clouded over time (due to airborne contaminants) which prevents a portion of the radiant energy emitted by the lamp from impinging upon the web. Thus, collection devices placed at the back of the lamp do not see this degradation, and an accurate measurement of energy radiated onto the web cannot be attained.
As discussed, due to the small physical space between the lamp and the web, it has been problematic to place a sensor between the web and the lamp which can withstand the hostile environment of intense heat and floating contaminants. Sensors which use protective covers are too bulky to be positioned between the lamp and the web. Collection devices which are small enough to be placed in the required position do not have protective covers and quickly degrade due to the airborne contaminants and high radiation surrounding the web. Additionally, sensors which contain electronic actuation components quickly degrade due to the high heat, radiation and humidity.
The invention is a pneumatically actuated energy collection device. The device includes a support which has an energy collector. A shutter is slidably attached to the support and can be positioned in a first position and a second position. Placing the shutter in the first position disposes the shutter so that it covers the collector. Placing the shutter in the second position disposes the shutter so that it does not cover the collector. The shutter is biased into one of the positions. A chamber is disposed next to the shutter so that when the chamber is pressurized, the pressurization overcomes the shutter bias and moves the shutter between the first position and the second position.
In one preferred embodiment of the energy collection device, when the shutter is placed in the second position, a curtain of pressurized air blows across the collector.